Myocardial and cerebral infarctions, conditions which are primarily the result of atherosclerotic lesions within the coronary and cerebral blood vessels, are the leading causes of death in Western civilization. A causal link between hypercholesterolemia and the premature development of atherosclerosis is well established. Hepatic biosynthesis is responsible for the majority of cholesterol transported in plasma lipoproteins. The rate-limiting enzyme of cholesterol biosynthesis, HMG CoA reductase, is therefore a prime target for drug intervention. Liver cells contain a protein kinase capable of almost totally inactivating HMG CoA reductase. This kinase is regulated allosterically by 5'-AMP and protein phosphorylation via a second kinase. The ultimate objective of this project is to discover novel, cell-permeable activators of the AMP-activated kinase as potential anti- hypercholesterolemic agents. In Phase I, substrates, assays and a purification scheme for the AMP-activated protein kinase were developed. Furthermore, a novel activator of this kinase was discovered in an initial screen of Oncogene Science's chemical file. Phase II of the project will include cloning and expression of the human AMP-kinase, development of a high-throughput kinase assay, and development of secondary cellular screens to determine the effects of activators of the AMP-kinase on intact cells and on HMG CoA reductase activity in vivo.